3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), that is, the improvement of an LTE Universal Mobile Telecommunications System (UMTS), has been introduced as 3GPP release 8. 3GPP LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) in downlink and uses Single Carrier-Frequency Division Multiple Access (SC-FDMA) in uplink. 3GPP LTE adopts Multiple Input Multiple Output (MIMO) having a maximum of 4 antennas. Recently, 3GPP LTE-Advanced (LTE-A), that is, the evolution of 3GPP LTE, is being discussed.
A Minimization Drive Test (MDT) is that service providers perform a test using UE instead of a vehicle for coverage optimization. Coverage varies depending on the location of a BS, the deployment of peripheral buildings, and a user use environment. Accordingly, a service provider needs to periodically perform a driving test, and lots of costs and resources are consumed. An MDT is that a service provider measures coverage using UE.
An MDT can be divided into a logged MDT and an immediate MDT. In accordance with the logged MDT, UE performs MDT measurement and then transfers logged measurement to a network at a specific point of time. In accordance with the immediate MDT, UE performs MDT measurement and then transfers measurement to a network when a report condition is satisfied. In the logged MDT, MDT measurement is performed in an RRC idle mode, whereas in the immediate MDT, MDT measurement is performed in an RRC connected mode.
A service provider can write a coverage map, indicating whether or not service is possible over the entire area to which service is provided by a service provider and a distribution of QoS, by synthesizing pieces of MDT measurement received from several pieces of UE and use the written coverage map in network operations and optimization. For example, when a report on a coverage problem for a specific area is received from UE, a service provider can enlarge the coverage of a corresponding area cell by increasing the transmission power of a BS that provides service to the corresponding area.
If one service provider manages a plurality of Public Land Mobile Networks (PLMNs) or a plurality of service providers manages a plurality of PLMNs in a wireless communication system, existing MDT measurement or a radio link failure report can be limited. This is because the execution of the MDT measurement or the radio link failure report can be limited to a cell corresponding to the Registered PLMN (RPLMN) of UE.
In the limited MDT measurement and/or radio link failure report in a wireless communication system under such a multiple PLMN environment, there may occur a problem in that the effectiveness of a measured or sensed report on a generated event is reduced because information about the measured or sensed report cannot be continuously reported to a network. Accordingly, there is a need for a method for guaranteeing the continuity of a measurement report according to MDT measurement and/or a report on information about a radio link failure in wireless communication under a multiple PLMN environment.